Need some advice.

[Kreekakon]

1) I don't think it'd make much of a difference either way personally. Do whatever you like on this one

2) My personal advice for this is that if your mod is going to be story based you should have a general idea of the entire plot from start to finish thought out before development even starts. You can leave out details for a later date, but I highly recommend that you at the very least have a basic outline of the entire plot.